IELTS

IELTS is designed to test the language ability of people who want to study or work where English is used as the language of communication.

Educational institutions, employers, professional registration bodies
and government immigration agencies often require proof of English
language skills as part of their recruitment or admission procedures. IELTS is widely accepted for these purposes. IELTS is designed to test the language ability of people who
want to study or work where English is used as the language of
communication. Over 3 million tests are taken each year.
(Source: http://www.cambridgeenglish.org/exams-and-tests/ielts)